The present invention relates to an exit flow silencer device for reducing turbulence in refrigerant flowing through a thermostatic expansion valve in an air conditioning system, such as in a vehicle.
Vehicle air conditioning systems typically include a compressor, condenser, and evaporator interconnected in a manner to remove heat from air in the interior compartment of the vehicle. Some vehicle air conditioning systems include a thermostatic expansion valve connected between the evaporator and condenser to reduce pressure and control flow of refrigerant flowing to the evaporator. By dropping pressure of refrigerant entering the evaporator, this enables the refrigerant to start boiling off or evaporate so that heat absorption can begin.
The thermostatic expansion valve has a capillary sensor that monitors refrigerant temperature flowing out of the evaporator. Expansion valves are described and calibrated to specific super heating settings. The purpose of the sensor and super heating setting is to allow the evaporator to get as cold as possible without freezing up and to assure that all liquid refrigerant entering the evaporator is a vapor when it exits.
Most automotive air conditioning compressors cannot accept liquid refrigerant because liquids cannot be compressed. Most systems with expansion valves will also have a thermostat control that assists in keeping the evaporator from icing up. The thermostat cycles the compressor when the evaporator approaches freezing, which is about the same time an expansion valve would start reducing flow of refrigerant. In combination, the expansion valve and the thermostat keep the evaporator as close to freezing as possible for maximum heat absorption. The expansion valve is designed to only regulate a solid liquid flow. Hissing sounds coming from the expansion valve indicate vapor bubbles passing through, which is normally the result of poor sub-cooling, a low charge or restriction in the high side. This also means the evaporator will not reach its optimum low temperature.
Most noise associated with the expansion valve occurs when sub-cooling is lost in the condenser. This may occur at vehicle idle or at low front end air flow and low compressor speed, which is run by the engine. In a vehicle having a rear air conditioning system, the thermostatic expansion valve in the rear part of the system experiences lower sub-cooling than the front because it is further from the condenser, and there are restrictions in the line.
It is desirable to provide an improved air conditioning system wherein noise from the thermostatic expansion valve is abated.
The invention provides a silencer screen positioned at the outlet of the thermostatic expansion valve to reduce turbulence in refrigerant flow exiting the thermostatic expansion valve.
More specifically, the invention provides an apparatus for manipulating the air temperature within an interior compartment of a vehicle. The apparatus includes a compressor, a condenser, and an evaporator interconnected in a manner to remove heat from air in the interior compartment. A thermostatic expansion valve is connected between the condenser and evaporator. The thermostatic expansion valve has an inlet and an outlet. A silencer screen is positioned at the outlet of the thermostatic expansion valve to reduce turbulence in refrigerant flow exiting the thermostatic expansion valve.
Preferably, the silencer screen is cylindrical in shape and supported by a cylindrical cage structure. Other shapes are contemplated within the scope of the present invention. The silencer screen is positioned within an end of an evaporator inlet tube which is connected to the thermostatic expansion valve.
The cylindrical cage structure preferably has a closed end and includes a flange which is connected to the outlet of the thermostatic expansion valve. The silencer screen is a mesh configuration having an opening size range between approximately 10 and 500 microns with 25% to 90% open flow area within the mesh configuration.
The silencer screen may be metal or plastic. The silencer screen may be connected to the cage structure, for example, by a plastic injection over-mold process.
The silencer screen is most preferably attached to an outlet of the thermostatic expansion valve adjacent a rear evaporator in a vehicle air conditioning system which includes front and rear evaporators.
The above objects, features, advantages, and other object, features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.